Requirement of the Caspase-3/CPP32 Protease Cascade for Apoptotic Death following Cytokine Deprivation in Hematopoietic Cells

Abstract

Hematopoietic cytokines transduce cell survival signals, which are distinct from the signals necessary for the stimulation of DNA synthesis. Recently, the Ras and phosphatidylinositol 3-kinase pathways have been shown to play important roles in preventing apoptosis in various cell types, e.g. hematopoietic cells and neuronal cells. Withdrawal of cytokine(s), in turn, results in rapid inactivation of these survival pathways and eventually leads to cell death accompanied by the hallmarks of apoptosis. However, the mechanism of cell death caused by cytokine deprivation has not been fully elucidated. In this study, we demonstrate that caspase-3/ CPP32, a member of the caspase/interleukin-1␤-converting enzyme family, is activated upon interleukin (IL)-3 deprivation in IL-3-dependent cells as well as IL-2 deprivation in IL-2-dependent cells. In addition, poly(ADPribose) polymerase, a cellular substrate for the caspase family proteases, was degraded into apoptotic fragments in both cell lines after cytokine removal. Furthermore, inhibition of a caspase family protease by synthetic peptides suppressed apoptotic death. These results indicate that the activation of a caspase-like protease(s) is required for the progression of apoptosis following cytokine deprivation. However, readdition of IL-3 did not restore the proliferative potential of the cells that survived in the presence of the peptide inhibitor after IL-3 depletion. Therefore, cellular commitment to apoptosis appears to precede the activation of a caspase-like protease(s).

Degradation of eukaryotic polypeptide chain initiation factor (eIF) 4G in response to induction of apoptosis in human lymphoma cell lines

“…The fact that several disparate inducers of apoptosis, which probably act by di erent mechanisms (Boix et al, 1998), all lead to the loss of eIF4G indicates that the pathways activated by these agents converge on this target protein. Low serum conditions activate apoptosis in immortalized or transformed cell lines (Kulkarni and McCulloch, 1994;Wang and Pandey, 1995;Kawanishi, 1997), probably by depriving the cells of growth factors necessary to promote cell cycle progression (Ohta et al, 1997); cycloheximide is also an e cient inducer of apoptosis in a variety of cell types, perhaps because it blocks the synthesis of one or more proteins essential for the prevention of apoptosis (Martin et al, 1990;Collins et al, 1991;Ledda-Columbano et al, 1992;Ishii et al, 1997); the CD95 (Fas) receptor acts by binding a number of proteins to the`death domain' located on its intracellular portion; etoposide interacts with DNA topoisomerase II and induces DNA strand breaks. The point of convergence of these pathways at the level of eIF4G is most likely the activation of one or more`executioner' caspases (Longthorne and Williams, 1997; Kamada et al, 1997;Cohen, 1997).…”

“…Apoptosis is characterized by a series of cellular changes that lead ultimately to cell death (Hale et al, 1996;Rowan and Fisher, 1997;Nagata, 1997;Salvesen and Dixit, 1997). An essential aspect of these events is the sequential activation of a number of proteases with limited substrate speci®cities, the caspases (Fearnhead et al, 1995;Tewari et al, 1995;Enari et al, 1996;Salvesen and Dixit, 1997;Cohen, 1997;Longthorne and Williams, 1997;Ohta et al, 1997). Intensive research in recent years has investigated the properties of these enzymes, the nature of some of their substrates, and their relative relationships in the protease cascades required for execution of the apoptotic programme.…”

Oxidative stress induces caspase-independent retinal apoptosis in vitro

“…Caspase-independent cell death has now been described in several models of apoptosis including glucocorticoid induced thymocyte cell death, 30 growth factor withdrawal in haematopoietic cell death, 32 etoptoside, 31 44,48 were retained. These studies have demonstrated that, at least in these models, several apoptotic events are not regulated by the caspases, and that while caspase activity may be sufficient for apoptotic cell death, it is not always necessary.…”

Anti-apoptotic function of Rac in hematopoietic cells

“…Given that this is true also in BaF3 cells, it is likely that Racmediated survival signals culminate in phosphorylation of BAD and thus induce anti-apoptotic actions of Bcl-X L . Moreover, a critical role of caspase 3, which serves as an essential e ector of apoptosis induced by various extracellular death signals, including Fas or tumornecrosis factor (TNF) stimulation, in death of hematopoietic cells upon IL-2 or IL-3 deprivation was recently reported (Ohta et al, 1997). Hence, it may be interesting to reveal the function of caspases in Ras or Rac-dependent cell survival.…”